Environment Canterbury defends call to keep lake closed to sea before floods hit

Monday, 5 May 2025

Flooding situation in Canterbury & Banks Peninsula, Monday. Flooded farmland near Ataahua.

Environment Canterbury has defended its failure to open Canterbury’s Te Waihora Lake Ellesmere before last week’s deluge caused widespread flooding.

The regional council’s director of science Tim Davie told RNZ: “Even if we had been able to open it… it wouldn’t have stayed open and we would have had the same issue.”

The lake remained closed to the sea on Monday, after attempts on Saturday and Sunday ended with it closing over on its own. Machinery was on site and an opening would happen as soon as weather and sea conditions allowed, the regional council’s website said.

Banks Peninsula MP Vanessa Weenink told RNZ on Monday the flooding had a “huge impact” on people who had to leave their homes or close their businesses.

Flooded farmers on the shores of Lake Ellesmere and Lake Forsyth were “pretty upset”.

Flooded farmland near Tai Tapu on Monday.

They had asked the lakes be opened to the sea ahead of the weather event. “People are feeling as though they weren’t listened to.”

Farmers around those areas were accustomed to water on their land, but sodden paddocks had a deep impact on farming, she said.

“[Some of] those paddocks will remain sodden for the winter. For some that’s hundreds of hectares.”

Motukarara - to the north east of Lake Ellesmere / Te Waihora in the Selwyn District experienced severe flooding.

ECan manages Te Waihora / Lake Ellesmere, the Christchurch City Council manages the opening of Lake Forsyth.

Davie told RNZ there were strict conditions under the nationally-set water conservation order about when ECan could open the lake to the sea.

He said they could override the rules “if there is an absolute emergency on” but the orange rain warning issued ahead of the rainfall “wasn’t particularly forecast for this area”.

The lake had to reach 1.13m, and it reached that on Tuesday afternoon.

“We were ready to go, but we weren’t able to open it.”

Tom Power has a big clean-up ahead after his farm was flooded on Thursday. He had urged the Christchurch City Council to earlier open nearby Lake Forsyth to the sea, to no avail.

ECan said last week the lake could only be opened in a joint decision with Ngāi Tahu. Consultation began last Monday and the decision to do so was reached on Tuesday afternoon - but by then the sea was too large to attempt an opening, as the sea would simply fill it in again.

“Even if we opened it, it wouldn’t have stayed open,” Davie told RNZ.

The council was managing the lake it for several lake values, including flooding. The lake level would need to rise another 2 metres before it opened naturally.

“We’re constantly looking to improve. We’ll look into this.”

Towards Little River, farmer Tom Power was facing a clean-up job he “shouldn’t have to do”.

It would take a few more days for the water to fully drain from his farm bordering Lake Forsyth.

Power had urged the Christchurch City Council to open the lake prior to the storm, which he said would have reduced the extent of the flooding.

So far he had seen a lot of logs, and other objects, lodged in fences with broken wires.

Power was hopeful in the council would be more receptive to opening Lake Forsyth in the future.

Council head of Three Waters Gavin Hutchinson said on Thursday diggers were on site but had to wait for southerly swells to drop to ensure the channel stayed open.